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Franz Wong
Franz Wong

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Monitor Java application with prometheus

#prometheus #java #tutorial

Prometheus provides JMX exporter which can export JVM information.

  1. Create JMX exporter configuration. Let's call it jmx_exporter_config.yml.
 --- rules: - pattern: "java.lang.*"
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2. Download JMX exporter

You can find the URL of JMX exporter jar file in Github repository.

https://github.com/prometheus/jmx_exporter

Here is the URL for 0.16.1

https://repo1.maven.org/maven2/io/prometheus/jmx/jmx_prometheus_javaagent/0.16.1/jmx_prometheus_javaagent-0.16.1.jar

3. Start your Java application

For example, your application is packaged as a jar file myapp_1.jar. jmx_prometheus_javaagent-0.16.1.jar and jmx_exporter_config.yml are saved in /app. We expose port 8080 to export metrics.

 java -javaagent:/app/jmx_prometheus_javaagent-0.16.1.jar=8080:/app/jmx_exporter_config.yml -jar myapp_1.jar
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4. Download Prometheus

You can find the URL of Prometheus in its official site.

https://prometheus.io/download/

Here is the URL of 2.33.0 (MacOS).

https://github.com/prometheus/prometheus/releases/download/v2.33.0/prometheus-2.33.0.darwin-amd64.tar.gz

5. Unzip Prometheus

After it is downloaded, unzip it and go to its directory.

 tar xvfz prometheus-*.tar.gz cd prometheus-*
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6. Update prometheus configuration

Add the following to the prometheus.yml (under scrape_configs). We adds label to help querying.

 - job_name: "apps" static_configs: - targets: ["localhost:8080"] labels: instance: 'myapp_1'
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The whole file should look like this.

 # my global config global: scrape_interval: 15s # Set the scrape interval to every 15 seconds. Default is every 1 minute. evaluation_interval: 15s # Evaluate rules every 15 seconds. The default is every 1 minute. # scrape_timeout is set to the global default (10s). # Alertmanager configuration alerting: alertmanagers: - static_configs: - targets: # - alertmanager:9093 # Load rules once and periodically evaluate them according to the global 'evaluation_interval'. rule_files: # - "first_rules.yml" # - "second_rules.yml" # A scrape configuration containing exactly one endpoint to scrape: # Here it's Prometheus itself. scrape_configs: # The job name is added as a label `job=<job_name>` to any timeseries scraped from this config. - job_name: "prometheus" # metrics_path defaults to '/metrics' # scheme defaults to 'http'. static_configs: - targets: ["localhost:9090"] - job_name: "apps" static_configs: - targets: ["localhost:8080"] labels: instance: 'myapp_1'
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7. Start Prometheus

 ./prometheus --config.file=prometheus.yml
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8. Query JVM information

http://localhost:9090/

Query jvm_memory_bytes_used{area="heap",instance="myapp_1"}

Here is the query result.

Query result

Or you prefer a graph (You may need to refresh the browser if you want to see the latest data)

Query result in graph

Here are other metrics you can try.

  • jvm_gc_collection_seconds_count

  • jvm_gc_collection_seconds_sum

  • jvm_memory_bytes_used -

  • jvm_memory_bytes_committed

  • jvm_memory_bytes_max

  • jvm_memory_bytes_init

  • process_cpu_seconds_total

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